A help from my little friends:
There’s a bit of potentially good news.  I have been working with the hypothesis that the infertility caused by inadequate consanguinity is mediated by a mechanism that involves the match in methylation patterns of parents and grandparents.  Too little match means too few offspring.

Vitamin B12 and folic acid are needed vitamins for humans.  And they increase the rate of methylation in mice.  A folic acid deficiency has been implicated in neural tube defects, a kind of embryonic abnormality.  In an effort to reduce this, the government requires that flour be fortified with folic acid added.  But that in isolation would be treacherous.  Both the vitamins are needed for DNA replication.  You can get an anemia from the lack of either one.  Vitamin B12 deficiency is also linked to a kind of neurological damage.  Consider what would happen to a person who was deficient in both.  Adding folate would restore DNA replication to a degree, but this would drive B12 down and could cause damage.  So although one might give B12 alone even in large doses, it would be unwise to give folic acid alone to everybody.  It might precipitate that neurological damage.  Accordingly the law requires both vitamins to be added to flour.

The potential problem is that these also raise methylation rates and conceivably could contribute to infertility, always a specter in humans and more so recently in developed countries.  The issue is a purely quantitative one.  The effect on fertility, if it exists at all, is unknown to anybody as far as what a hazardous dose might be.  We’ll know soon.  The first people who were born, and thus who underwent embryonic and fetal development, under the new regime are just reaching teenage. 

But according to recent work, (Microbes maketh the man ECONOMIST vol. 404 no. 8798 August 18, 2012 page 9 and Me, myself and us page 99 of the same issue) gut flora, bacteria living in the gastro intestinal tract, make both B12 and folic acid for us.  This is news to me, although I doubt it is news to experts in the field.  Just how much they make is not known to me.  But maybe, just maybe, they make enough and are responsive enough to dietary B12 so that they keep the balance just right.  That would be a lucky good thing, one less disaster to worry about.

The current thinking is rather dramatizing the contribution of our gut flora.  It is suggested that our DNA lines transmitted by gametes is not the only DNA we inherit.  This leads to people suggesting that a person is not an organism but is one part of a larger organism that includes the flora.  This raises a rather untroubling question about just what it is to be human.  If the teamwork also means that there will continue to be human beings, at least to have humans who live in a high tech society, so much the better.

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